The present invention relates to an optical device, more particularly, an optical device of a full-size or magnified image forming type which can be used for a lightweight low-profile flat display.
Recently lightweight low-profile flat displays such as LCDs and PDPs have been becoming widespread, and larger screens of higher definition are expected.
However, it is difficult to apply a micromachining (micropatterning) process, which is used for LCDs and the like, to a large-size substrate from the viewpoint of yield. Taking the yield into account, it is considered to be desirable to combine several small-size substrates to form a large screen.
For this purpose, there can be proposed a method of producing a large screen by connecting a plurality of small-sized substrates without gaps. However, this method involves great difficulty during manufacture in view of precise alignment, complicated wiring and others.
Also a so-called multi-panel display is proposed which is a method of arranging a plurality of already assembled displays of small size, placing optical devices for magnifying images in front of the respective displays and connecting respective images of the displays without boundary lines for a large screen. This multi-panel display is considered promising since magnification is easy. For realization of the multi-panel display, optical devices of a magnified image formation system with a large aperture (e.g., 18 cmxc3x9724 cm).
As such an optical device of the magnified image formation system, is conventionally proposed a combination of a rod lens array having the function of forming erect full-size images and a Fresnel lens for magnifying images.
However, since the rod lens array is typically produced of a large number of cylindrical glass lenses in a bundle, the rod lens array with a large aperture is heavy and expensive.
For further spread of multi-panel displays, there is a demand for a reduction in the price and a decrease in the weight of optical devices. Further, the Fresnel lens has a problem in that, if is magnifying power is increased, utilization efficiency decreases in a peripheral part of the lens and brightness becomes uneven.
An object of the present invention is to provide an optical device of an erect full-size image formation system or magnified image formation system with use of lens substrates formed with cylindrical lens arrays on a front and a rear face thereof.
The present invention provides an optical device characterized by including an image formation unit having a plurality of lens substrates each formed with lens arrays on both a front face and a rear face thereof; and a display unit disposed on an object side with respect to the image formation unit for displaying an image to be projected by the image formation unit, wherein, on each of said plurality of lens substrates, the lens array on both the front and rear faces are cylindrical lens arrays, and the generatrix of the cylindrical array formed on the front face and the generatrix of the cylindrical array formed on the rear face are orthogonal to each other.
Further said plurality of lens substrates may be constructed of a first lens substrate; a second lens substrate having the same lens shape as that of the lens array on the first lens substrate and disposed adjacently to the first lens substrate so that the generatrix of the lens array on a face opposing to the first lens substrate is parallel to the generatrix of the lens array on an opposing face of the first lens substrate; a third lens substrate disposed adjacently to the first lens substrate on a different side from a second lens substrate side with respect to the first lens substrate so that the generatrix of the lens array on a face opposing to the first lens substrate is orthogonal to the generatrix of the lens array on an opposing face of the first lens substrate; and a fourth lens substrate having the same lens shape as that of the lens array on the third lens substrate and disposed adjacently to the second lens substrate on a different side from a first lens substrate side with respect to the second lens substrate so that the generatrix of the lens array on a face opposing to the second lens substrate is orthogonal to the generatrix of the lens array on an opposing face of the second lens substrate. Thereby obtained is an optical device of the erect full-size image formation system.
Further the present invention provides an optical device further comprising a Fresnel concave lens disposed between the image formation unit and the display unit adjacently to a display face of the display unit.
Here, the plurality of lens substrates may be so constructed that it is composed of a first lens substrate; a second lens substrate disposed adjacently to the first lens substrate so that the generatrix of the lens array on a face opposing to the first lens substrate is parallel to the generatrix of the lens array on an opposing face of the first lens substrate; a third lens substrate disposed adjacently to the first lens substrate on a different side from a second lens substrate side with respect to the first lens substrate so that the generatrix of the lens array on a face opposing to the first lens substrate is orthogonal to the generatrix of the lens array on an opposing face of the first lens substrate; and a fourth lens substrate disposed adjacently to the second lens substrate on a different side from a first lens substrate side with respect to the second lens substrate so that the generatrix of the lens array on a face opposing to the second lens substrate is orthogonal to the generatrix of the lens array on an opposing face of the second lens substrate, and that the pitch of the lens array on lens substrate disposed nearest to the display unit is the smallest and the pitches of the lens arrays on the lens substrates are set to be gradually larger as the lens substrates are farther from the display unit. With this construction, obtained is an optical device of the magnified image formation system.